| The bearing capacity of bridge structure will decrease and the damage will accumulate inevitably under environmental erosion, material aging, effects of long-term load, fatigue effects and mutation effect. The remaining service life of bridge is standing an severe test. How to evaluate the state of steel bridge scientifically and how to analyze residual fatigue life of the aged highway bridge steel need to be solved at once. In this paper,combined with a health detection project on a steel truss bridge in Lanzhou city, the evaluation for remaining fatigue life of highway steel bridge in service is studied as follows:(1) This paper introduces the basic concepts of research fatigue and remaining life, the importance of steel bridge fatigue problems and status; Some basic concepts and methods of the fatigue analysis is briefly described. It also introduces the method and procedure of the evaluation of residue fatigue life according to the theory of nominal stress method.(2) The anti-fatigue design methods of highway bridge steel is illustrated briefly and the existing problems of anti-fatigue design code is pointed out. With some examples to introduce the application of highway bridge steel anti-fatigue design.(3) Combined with example of a steel truss bridge which is monitored and health-assessed in Lanzhou, the method of bridge structure fatigue surplus life's assessment is discussed in the application deeply.(4) The finite element model of the bridge is found. The model is checked through comparing the theoretical stress-strain to actual results, and all of these lay a foundation for the fatigue life of bridge.(5) How to calculate the operating stress spectrum of the bridge according to the current strain-time history curve is discussed and the practical calculation method of fatigue accumulating and the rest of fatigue life is put forward in this paper.
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